JP5045236B2 - Multilayer sheet - Google Patents

Description

The present invention relates to a multilayer sheet including an optical sheet having a plurality of recesses on one main surface.

  Patent Document 1 describes an optical sheet used in a liquid crystal display device. This optical sheet is a resin layer provided with a plurality of recesses on one main surface. Each recess has a triangular pyramid shape. Moreover, the opening of each recessed part has an equilateral triangle shape.

If this optical sheet is used, the spread angle of light can be made substantially equal in all directions. However, it is difficult to obtain a complicated optical effect with an optical sheet in which a plurality of concave portions each having a triangular pyramid shape are provided on one main surface.
JP-A-8-271889

An object of the present invention is to provide a multilayer sheet including an optical sheet that can achieve a complicated optical effect and is easy to design.

According to an aspect of the present invention, a plurality of grooves adjacent to each other in the width direction are provided with a resin layer provided on one main surface, and each side wall of the plurality of grooves has an opening of the groove compared to the bottom. A pair of inclined surfaces which are inclined at least partially with respect to the main surface so as to be wide, and are inclined in the lengthwise direction with respect to the main surface at the bottom of each of the plurality of grooves. There is provided an optical sheet characterized in that each of the optical sheets is provided with a plurality of protrusions which are included and are spaced apart from each other in the length direction of the groove.

  Note that the term “film” and the term “sheet” may be properly used depending on the thickness, but here, no distinction is made according to the thickness.

According to the present invention, a multilayer sheet including an optical sheet that can achieve a complicated optical effect and is easy to design is provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same referential mark is attached | subjected to the component which exhibits the same or similar function, and the overlapping description is abbreviate | omitted.

  FIG. 1 is a perspective view schematically showing an optical sheet according to one embodiment of the present invention. FIG. 2 is an enlarged perspective view showing a part of the optical sheet shown in FIG. 3 is a cross-sectional view of the optical sheet shown in FIG. 2 taken along the line III-III. 4 is a cross-sectional view of the optical sheet shown in FIG. 2 taken along line IV-IV. FIG. 5 is a cross-sectional view taken along line VV of the optical sheet shown in FIG.

  1 to 5, the X direction and the Y direction are parallel to the main surface of the optical sheet 10 and intersect each other. The Z direction is a direction orthogonal to the X direction and the Y direction.

  The optical sheet 10 shown in FIGS. 1 to 5 is, for example, a diffusion sheet or a viewing angle control sheet. The optical sheet 10 is light transmissive.

  A plurality of grooves 11 adjacent to each other in the width direction, that is, the Y direction are provided on one main surface of the optical sheet 10. Each of these grooves 11 has a shape extending in the X direction. The groove 11 may be linear as shown in FIGS. 1 and 2 or may be curved. For example, the groove 11 may meander.

  The pair of side walls of each groove 11 is at least partially inclined with respect to the previous main surface so that the opening of the groove 11 is wider than the bottom. In each groove 11, an angle θ <b> 1 formed by the inclined portion of the side wall with respect to the previous main surface is within a range of 40 ° to 60 °, for example. When the angle θ1 is small, the effect of controlling the light spread angle is small. When the angle θ1 is large, the total light transmittance is lowered, and stamper grinding described later becomes difficult. In each groove 11, the angle formed by the inclined portion of one side wall with respect to the previous main surface and the angle formed by the inclined portion of the other side wall with respect to the previous main surface are as shown in FIGS. May be equal to or different from each other.

  These grooves 11 may have the same structure or different structures. For example, the angle θ1 and / or the depth D may be different between a part of the groove 11 and another part.

  The groove 11 may be a V-shaped groove as shown in FIGS. 1 to 3 or a groove having another shape such as a U-shaped groove. The side wall of the groove 11 may include a vertical surface and / or a curved surface. Further, the groove 11 may include a bottom surface substantially parallel to the previous main surface.

  A plurality of convex portions 12 are provided at the bottom of each of the grooves 11. In each groove 11, these convex portions 12 are arranged away from each other in the length direction of the groove 11, that is, in the X direction.

  Each convex portion 12 includes a pair of inclined surfaces inclined in the opposite direction in the X direction with respect to the previous main surface. In the optical sheet 10 shown in FIGS. 1 to 5, each convex portion 12 is formed of a pair of isosceles triangles.

  The angle θ2 formed by the inclined surface of each convex portion 12 with respect to the previous main surface is, for example, in the range of 40 ° to 60 °. When the angle θ2 is small, the effect of controlling the light spread angle is small. When the angle θ2 is large, the total light transmittance is lowered, and stamper grinding described later becomes difficult.

  The angle θ2 and the angle θ1 may be the same or different. Moreover, in each convex part 12, the angle which one inclined surface makes with respect to the previous main surface, and the angle which the other famous inclined surface makes with respect to the previous main surface are shown in FIGS. As shown, they may be equal or different.

  These convex portions 12 may have the same structure or different structures. For example, the angle θ2 and / or the height H may be different between a part of the convex part 12 and another part. Further, the distance d between the convex portions 12 adjacent in the X direction may be constant or may vary depending on the location.

  As shown in FIGS. 1, 2, and 5, the convex portion 12 does not need to include a surface parallel to the previous main surface, and may include such a surface. Further, the inclined surface of the convex portion 12 may be a flat surface or a curved surface.

  The height H of the convex portion 12 is equal to or lower than the depth D of the groove 11. When the height H is lower than the depth D, for example, when the optical sheet 10 is overlapped with the optical film, the convex portion 12 can be prevented from coming into contact with the optical film. Therefore, in this case, it is difficult to cause deformation and / or damage of the convex portion 12 due to contact with the optical film.

  When the height H is equal to the depth D, for example, when the optical sheet 10 is overlapped with the optical film to close the opening of the groove 11, the space in the groove 11 is divided by the convex portion 12. On the other hand, when the height H is lower than the depth D, even if the optical sheet 10 is overlapped with the optical film to close the opening of the groove 11, the space in the groove 11 is divided by the convex portion 12. It will never be done. Therefore, when the latter structure is employed, undesired adhesion to the optical film is less likely to occur than when the former structure is employed.

  In addition, when the groove 11 is a V-shaped groove, each convex portion 12 is constituted by a pair of isosceles triangles, and the height H is equal to the depth D, a plurality of concave portions each having a dormitory shape are formed on one main surface. The optical sheet 10 arranged in the X direction and the Y direction is obtained. Further, when the groove 11 is a V-shaped groove, each convex portion 12 is constituted by a pair of isosceles triangles, and the height H is lower than the depth D, each of them is a half gable as shown in FIGS. The optical sheet 10 in which a plurality of concave portions having a shape are arranged in the X direction and the Y direction on one main surface is obtained.

  In this optical sheet 10, the groove 11 mainly affects the spread of light in a plane perpendicular to the X direction. On the other hand, the convex portion 12 mainly affects the spread of light in a plane perpendicular to the Y direction. As described above, according to the optical sheet 10, the spread of light in the plane perpendicular to the X direction and the spread of light in the plane perpendicular to the Y direction can be controlled by different structures. Can be achieved.

The optical sheet 10 is easy to design as described below.
Assuming that the convex portion 12 is omitted, the influence of the groove 11 on the spread of light in a plane perpendicular to the X direction is easily calculated from the angle θ1, the depth D, and the refractive index n of the optical sheet 10. it can. Further, assuming that the groove 11 is omitted, the influence of the convex portion 12 on the spread of light in a plane perpendicular to the Y direction is easily obtained from the angle θ2 , the height H, the refractive index n, and the distance d. Can be calculated. By using these calculation results, it is possible to calculate the influence of the groove 11 and the convex portion 12 on the spread of light in the plane perpendicular to the X direction and the spread of light in the plane perpendicular to the Y direction. Easy.

  Therefore, the structure to be adopted for the groove 11 and the convex portion 12 can be easily calculated from the optical effect required for the optical sheet 10. That is, the optical sheet 10 is easy to design.

  For example, even if the distance d is set to zero, by making the height H sufficiently small, the spread of light in the plane perpendicular to the X direction is compared with the spread of light in the plane perpendicular to the Y direction. Larger optical sheet 10 can be obtained. However, it is difficult to form the convex portion 12 having a small height H with high dimensional accuracy.

  On the other hand, if the convex portions 12 adjacent to each other in the X direction are separated from each other, the light spread in a plane perpendicular to the X direction is perpendicular to the Y direction without excessively reducing the height H. A larger optical sheet 10 can be obtained compared to the spread of light in a smooth plane. Therefore, it is possible to prevent the optical characteristics of the optical sheet 10 from greatly deviating from the design value due to the dimensional accuracy of the convex portion 12.

  Further, when the grooves 11 are separated from each other, the spread of the light incident on the portion corresponding to the region between the grooves 11 of the optical sheet 10 cannot be controlled. On the other hand, when the grooves 11 are adjacent to each other, the spread of all incident light can be controlled.

  The area | region corresponding to the boundary between the grooves 11 among the front main surfaces of the optical sheet 10 may be curved when viewed from the X direction. If it carries out like this, while the component overlapped with the optical sheet 10 becomes difficult to be damaged, the optical sheet 10 itself becomes difficult to be damaged. Further, when the optical sheet 10 and the layered component are bonded together, the bonding becomes easy.

  The optical sheet 10 may have a single layer structure or a multilayer structure. The optical sheet 10 having a single layer structure is made of, for example, a resin layer. An optical sheet having a multilayer structure is formed, for example, by forming a resin layer or an inorganic layer on a substrate.

  Examples of the material of the resin layer include thermoplastic resins such as acrylic resins, polycarbonate resins, styrene resins, and acrylic styrene copolymer resins, and thermoplastic resins such as polyethylene terephthalate resins, or ultraviolet curable resins and electron beam curable resins. An ionizing radiation curable resin can be used. As a material for the base material, a material having excellent stability as compared with the resin layer or the inorganic layer can be used. Typically, a polyethylene terephthalate resin is used as the base material. As a material for the inorganic layer, for example, an inorganic material such as silicate can be used.

  The optical sheet 10 can be formed by, for example, a method using a stamper. For example, a thermoplastic resin is used as a material for the resin layer, and a heated stamper is pressed against the resin layer. Thereby, the uneven structure of the stamper is transferred to the resin layer. Alternatively, an ionizing radiation curable resin is interposed between the substrate and the stamper, and the ionizing radiation curable resin is irradiated with ionizing radiation in this state. The optical sheet 10 is obtained by removing the ionizing radiation curable resin thus cured together with the base material from the stamper.

  As the stamper, for example, a flat stamper or a roll stamper can be used. The method using the roll stamper is superior in productivity as compared with the method using the flat stamper.

  The roll stamper can be manufactured, for example, by the following method. First, a roll whose roll surface is made of a copper plating layer is prepared. Next, the roll surface is cut using a cutting tool. Thereby, the groove | channel of the pattern corresponding to the boundary between the grooves 11, and the groove | channel or recessed part of the pattern corresponding to the convex part 12 are formed in a roll surface.

  In the optical sheet 10, as described above, the angles θ1 and θ2 are in the range of 40 ° to 60 °, for example. In this way, the spread angle of the transmitted light can be made particularly narrow and a high total light transmittance can be achieved.

  FIG. 6 is a graph showing an example of the influence of the uneven structure provided in the optical sheet on the spread angle of transmitted light. In the figure, the horizontal axis represents the angles θ1 and θ2, and the vertical axis represents the spread angle of the transmitted light. The “maximum divergence angle” indicates the maximum value of the divergence angle obtained when the optical sheet 10 is irradiated with parallel light from the flat surface side and the divergence angle of the transmitted light is measured while changing the incident angle. “Minimum divergence angle” indicates the minimum value of the divergence angle obtained under the same conditions. Here, for simplification, the distance d is set to zero, the angles θ1 and θ2 are made equal, and the depth D and the height H are made equal.

As shown in FIG. 6, when the angles θ1 and θ2 are about 40 ° or more , the maximum spread angle can be remarkably reduced. Moreover, if the angles θ1 and θ2 are, for example, about 60 ° or less, a high total light transmittance can be achieved. Therefore, when the angles θ1 and θ2 are in the range of about 40 ° to about 60 °, most of the light emitted from the light source can be emitted in a specific direction on the optical sheet 10.

This optical sheet 10 can be used as a part of a multilayer sheet.
FIG. 7 is a cross-sectional view schematically showing an example of a multilayer sheet including the optical sheet shown in FIGS. FIG. 8 is a cross-sectional view schematically illustrating another example of a multilayer sheet including the optical sheet illustrated in FIGS. 1 to 5. FIG. 9 is a cross-sectional view schematically showing still another example of the multilayer sheet including the optical sheet shown in FIGS.

  The multilayer sheet shown in FIGS. 7 to 9 includes the optical sheet 10 described with reference to FIGS. 1 to 5 and the optical layer 20.

  In the multilayer sheet shown in FIG. 7, the optical layer 20 covers the surface of the optical sheet 10 on which the grooves 11 are provided. In this multilayer sheet, grooves and projections are provided on the surface of the optical layer 20 corresponding to the surface of the optical sheet 10. The optical layer 20 can be formed by, for example, a vapor deposition method. In this multilayer sheet, the optical sheet 10 side may be the light incident side, and the optical layer 20 side may be the light incident side. As the optical layer 20, for example, a transparent layer, a light absorption layer, or a light reflection layer having a refractive index different from that of the optical sheet 10 can be used.

  In the multilayer sheet shown in FIG. 8, the optical layer 20 covers the surface of the optical sheet 10 on which the grooves 11 are provided. In this multilayer sheet, the surface of the optical layer 20 is a flat surface. The optical layer 20 can be formed by, for example, a solution coating method. Alternatively, a film-like optical layer 20 may be prepared, and this and the optical sheet 10 may be bonded together via a pressure-sensitive adhesive layer or an adhesive layer. In this multilayer sheet, the optical sheet 10 side is typically the light incident side. As the optical layer 20, for example, a light absorption layer, a light reflection layer, or a light scattering layer can be used.

  In the multilayer sheet shown in FIG. 9, the optical layer 20 covers the back surface of the surface on which the groove 11 of the optical sheet 10 is provided. The optical layer 20 can be formed by, for example, a vapor deposition method or a solution coating method. Alternatively, a film-like optical layer 20 may be prepared, and this and the optical sheet 10 may be bonded together via a pressure-sensitive adhesive layer or an adhesive layer. In this multilayer sheet, the optical sheet 10 side is typically the light incident side. As the optical layer 20, for example, a light absorption layer, a light reflection layer, or a light scattering layer can be used.

  As a material for the transparent layer, for example, the resin exemplified for the optical sheet 10 or an inorganic material such as glass and silicone rubber can be used.

  As a material for the light absorption layer, for example, colored pigments such as carbon and metal salts, dyes, or combinations thereof can be used.

  As a material of the light reflection layer, for example, metal materials such as silver, aluminum, and alloys thereof can be used. As a material for the light reflecting layer, a mixture of a white pigment such as titanium dioxide, barium sulfate and magnesium oxide and a binder resin may be used.

  As a material for the light scattering layer, for example, a mixture of fine particles and a binder resin having a refractive index different from that of the fine particles can be used. As the material for the fine particles, an inorganic material such as alumina and silica, or an organic material such as an acrylic resin, a styrene resin, a polycarbonate resin, and an acrylic styrene copolymer resin can be used. Examples of the binder resin include acrylic resin, polyurethane resin, polyester resin, polyvinyl chloride resin, polyvinyl acetate resin, polystyrene resin, polycarbonate resin, polypropylene resin, polyarylate resin, polysulfone resin, polyethersulfone resin, epoxy resin, Polyolefin resin, fluorinated polyimide resin, norbornene resin, nylon resin or a mixture thereof can be used. The size of the fine particles is made smaller than the opening width of the groove 11, the depth D of the groove 11, and the distance between the centers of the convex portions 12 adjacent in the X direction. Typically, the size of the fine particles is made smaller than the opening width of the groove 11, the depth D of the groove 11, and the distance d.

  Even if each of the fine particles and the binder resin is colorless, the refractive index difference between the binder resin and the fine particles and / or the particle size of the fine particles is appropriately set, for example, the average particle size of the fine particles is set to 5 μm or less. This makes it possible to make the light scattering layer appear bluish. However, when the particle size of the fine particles is reduced, backscattering increases, and as a result, the total light transmittance tends to decrease.

  These multilayer sheets can be variously modified. For example, the multilayer sheet shown in FIG. 9 may include a sound insulating material layer made of, for example, metal or glass instead of or in addition to the optical layer 20. If it carries out like this, the function as a sound insulating material can be provided to a multilayer sheet. In addition, the multilayer sheet may be a glass layer, a plastic film, a diffusion layer, an anti-reflection layer, an anti-glare layer, a low reflection (low) instead of or in addition to the optical layer 20. Layers such as a reflection layer and an anti-static layer may be included.

  The optical sheet 10 and the multilayer sheet described above can be used in various applications. For example, the optical sheet 10 and the multilayer sheet can be used as a diffusion sheet for a lighting device, or for the purpose of controlling the viewing angle of a liquid crystal display and / or suppressing luminance unevenness. In addition, the multilayer sheet described above can be used as a light-absorbing sheet with extremely small light reflection in the front direction, as a light-reflecting sheet used in corner poles, or as a design sheet.

Examples of the present invention will be described below.
(Example)
The multilayer sheet shown in FIG. 9 was produced by the following method.

  First, a polyethylene terephthalate film having a thickness of 75 μm and a refractive index of 1.51 was prepared. An ultraviolet curable resin was applied on one main surface of the film, and ultraviolet rays were irradiated while pressing a roll stamper on the coated surface. As described above, the optical sheet 10 shown in FIGS. 1 to 5 was obtained.

  Here, as the ultraviolet curable resin, one having a refractive index after curing of 1.556 was used. The groove 11 had a width W of 50 μm, a depth D of 23.1 μm, and an angle θ1 of 42.74 °. The convex portion 12 has a pitch P in the X direction of 50 μm, a height H of 20.3 μm, and an angle θ2 of 44.4 °.

  Next, an ink containing an acrylic resin and a black pigment was applied to the back surface of the surface on which the groove 11 of the optical sheet 10 was provided. The ink layer was cured to form a light absorption layer as the optical layer 20.

  As described above, the multilayer sheet shown in FIG. 9 was completed. Hereinafter, this multilayer sheet is referred to as “sheet A”.

(Comparative example)
In this example, a multilayer sheet is produced in the same manner as described for the sheet A except that a polyethylene terephthalate film having a thickness of 75 μm and a refractive index of 1.51 is used instead of the optical sheet 10. did. That is, in this example, the groove 11 and the convex portion 12 are omitted from the optical sheet 10. Hereinafter, this multilayer sheet is referred to as “sheet B”.

Next, the sheet A was irradiated with light from the normal direction on the back surface of the surface provided with the light absorption layer, and the transmittance was examined. As a result, the total light transmittance was 0.16%.
Moreover, the brightness | luminance was measured about reflected light on the same conditions. The result is shown in FIG.

  FIG. 10 is a graph showing the relationship between the observation angle and the luminance. In the figure, the horizontal axis indicates the observation angle, and the vertical axis indicates the relative luminance.

As shown in FIG. 10, the sheet B exhibited high relative luminance within a wide angle range. In contrast, the sheet A exhibited a high relative luminance within an angle range of about 15 ° or less, but the relative luminance was extremely low within an angular range larger than that. From this result, it can be seen that the sheet A is superior in performance as an antireflection sheet as compared with the sheet B.
The invention described in the original claims is appended below.
[1] A plurality of grooves adjacent to each other in the width direction are provided on one main surface, and the side walls of each of the plurality of grooves are formed with respect to the main surface such that the opening of the groove is wider than the bottom. Each of the plurality of grooves, the bottom of each of the plurality of grooves includes a pair of inclined surfaces inclined in opposite directions with respect to the main surface and in the length direction of the grooves. The optical sheet is provided with a plurality of convex portions arranged separately from each other.
[2] The optical sheet according to item 1, wherein each of the plurality of grooves is a V-shaped groove.
[3] The optical sheet according to item 1 or 2, wherein in each of the plurality of grooves, the plurality of convex portions are lower than the depth of the groove.
[4] In each of the plurality of grooves, an angle formed by each of the pair of inclined surfaces with respect to the main surface is an angle formed by a portion of the side wall inclined with respect to the main surface with respect to the main surface. The optical sheet according to any one of Items 1 to 3, wherein the optical sheet is different from the above.
[5] The region according to any one of claims 1 to 4, wherein when viewed from the length direction, a region corresponding to a boundary between the plurality of grooves in the main surface is curved. Optical sheet.
[6] The optical sheet according to any one of items 1 to 5, and a transparent layer covering the one main surface or the other main surface of the optical sheet, wherein the optical sheet is light transmissive. And the transparent layer has a refractive index different from that of the optical sheet.
[7] The optical sheet according to any one of items 1 to 5, and a light absorption layer covering the other main surface of the optical sheet, wherein the optical sheet is light transmissive. Multi-layer sheet.
[8] The optical sheet according to any one of items 1 to 5, and a light reflecting layer covering the other main surface of the optical sheet, wherein the optical sheet is light transmissive. Multi-layer sheet.
[9] A multilayer sheet comprising the optical sheet according to any one of items 1 to 5 and a light absorbing layer covering the one main surface.
[10] A multilayer sheet comprising the optical sheet according to any one of items 1 to 5 and a light reflecting layer covering the one main surface.

1 is a perspective view schematically showing an optical sheet according to one embodiment of the present invention. The perspective view which expands and shows a part of optical sheet shown in FIG. Sectional drawing along the III-III line of the optical sheet shown in FIG. Sectional drawing along the IV-IV line of the optical sheet shown in FIG. Sectional drawing along the VV line of the optical sheet shown in FIG. The graph which shows the example of the influence which the uneven structure provided in an optical sheet has on the spreading angle of transmitted light. Sectional drawing which shows roughly an example of the multilayer sheet containing the optical sheet shown in FIG. 1 thru | or FIG. Sectional drawing which shows schematically the other example of the multilayer sheet containing the optical sheet shown in FIG. 1 thru | or FIG. Sectional drawing which shows schematically the further another example of the multilayer sheet containing the optical sheet shown to FIG. 1 thru | or FIG. The graph which shows the relationship between an observation angle and a brightness | luminance.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Optical sheet, 11 ... Groove, 12 ... Convex part, 20 ... Optical layer.

Claims (2)

A plurality of grooves adjacent to each other in the width direction are provided on one main surface, and each side wall of each of the plurality of grooves is at least partially with respect to the main surface such that the opening of the groove is wider than the bottom. Each of the plurality of grooves includes a pair of inclined surfaces inclined in opposite directions in the length direction with respect to the main surface and spaced apart from each other in the length direction of the grooves. An optical sheet provided with a plurality of convex portions arranged in a row, a light absorption layer containing carbon covering the other main surface of the optical sheet, and the optical sheet being light transmissive A multilayer sheet characterized by that. A plurality of grooves adjacent to each other in the width direction are provided on one main surface, and each side wall of each of the plurality of grooves is at least partially with respect to the main surface such that the opening of the groove is wider than the bottom. Each of the plurality of grooves includes a pair of inclined surfaces inclined in opposite directions in the length direction with respect to the main surface and spaced apart from each other in the length direction of the grooves. A multilayer sheet comprising: an optical sheet provided with a plurality of convex portions arranged in a row; and a light-absorbing layer covering the one main surface and containing carbon.

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